Textile-based electrodes consisting of electrically conductive wires or electrically conductive yarns with metal fibers surrounded by a region of electrically nonconductive textile fibers can be integrated with a wearable article, such as a garment. The wires or electrically conductive yarns with metal fibers are incorporated into the wearable article. The wearable article is then adapted to receive or transmit electrical impulses to or from the wearer and, in turn, to or from an electrical device. The patent document WO 01/02052, assigned to Bekaert, discloses such a wearable article.
Wearable textile-based sensors made from yarns with metal fibers for sensing or otherwise reporting the heart rate (the pulse) of the wearer are disclosed in patent document WO 02/071935, assigned to RTO Holding OY.
Patent document WO 03/094717, assigned to Koninklijke Philips Electronics NV, discloses a textile article that is provided with a region of skin contacting electrodes that are fully integrated within a textile article. The disclosed textile article takes the form of a “bra or a ladies top,” which is otherwise electrically nonconducting. The article is provided with partially overlapping layers of electrically conductive material, which may be made from metal fibers, and electrically insulative material arranged to partially cover and electrically isolate the electrically conductive material.
Patent document WO 2004/006700, assigned to Tefron Ltd., discloses a circularly knit garment having an inner surface electrically-conductive region, which can be metallic, disposed close to the wearer's skin. The inner electrically-conductive region cooperates to conduct electrical signals to an outerlying electrically-conductive region. Such electrical signals may include the heart rate coming from the wearer or an electro-stimulation means going to the wearer.
Each of these patent documents relates an objective to provide an electrically-conductive region, which can comprise metallic wires or fibers, and which can function as an electrode integrated with a garment, a belt, or other wearable article of traditional textile construction. Generally, these patent documents disclose an electrically-conductive region that is otherwise electrically isolated from the remainder of the garment or wearable. These regions may be knitted into the garment. Furthermore, these patent documents disclose placing at least one electrically-conductive region of the garment in close contact with the skin of the wearer. As a result, the electrode, formed by this electrically conductive region in contact with the skin, provides a pick-up point for electrical signals generated within the corpus of the wearer. Alternatively, such an electrode provides a point of contact on the skin to receive an electrical signal generated externally to the wearer. In summary, these patent documents provide means to communicate electrical signals to or from the corpus of a garment wearer.
In addition, these patent documents generally disclose at least a second textile electrode. More often, the second electrode is integrated with the garment and located at or near an exterior surface of the garment. The second electrode can also be advantageously placed overlying the electrode in skin contact, while also having a portion of the garment's electrically insulating materials of construction therebetween. Where an electrical connection between the electrode(s) in skin contact and the exterior electrode(s) is desired, such connection can be established using metallic wires. Alternatively, the skin contact electrode can be folded over in such a manner as to form the exterior surface electrode continuously.
U.S. Pat. Nos. 7,308,294 and 7,474,910 assigned to Textronics Inc. show other wearable textile-based sensors for monitoring biophysiological signals.
Where an electrical connection between a garment-integrated electrode in skin contact with the wearer and a garment-integrated exterior electrode is established using metallic wires or yarns with metal fibers, certain limitations may exist. Such limitations can result during the knitting process because of the nature of the tools used. For example, needle wear and breakage can occur due to metal-to-metal contact between the needle and the metallic wires or yarns with metal fibers. To increase the efficiency and productivity of knitting machines, an increase in operating speed is also desired. Such an increase, however, can also result in increased needle wear. Depending on the type of yarns selected, wear can also be attributed to contaminants within the yarns, affecting not only needles but also the yarn carriers, sinkers, and cams.
For example, for high speed knitting on circular knitting machines, needles are frequently replaced due to the repetitive contact between metallic wires or yarns with metal fibers and the metallic needles used during manufacture of the wearable. Needle wear can result from the free end of the latch engaging the hook of the needle when the latch swings to the closed position during the movement of the needle to a lowered stitch loop forming position. Wear of the needle can also occur when the latch swings to the fully open position as the needle is raised to clear the stitch loop below the latch. The impact of the latch against the needle can also cause metal fatigue and latch failure, in some cases.
Needle wear can also result due to the properties of the yarns used. For example, yarns made from metal coated fibers are rigid and have very little “give,” resulting in wear on the knitting elements. This especially occurs when the metal coated fiber is first pulled into the knitted structure. Wear also can occur when spun yarns are made from natural or chemical fibers used during manufacture of the wearable article. Some chemical fibers may, for example, have matting agents that generate needle wear. In addition, spun yarns made from natural fibers may contain foreign particles due to how the fibers are cultivated, harvested, and the cleaning methods used after harvesting. A frequent contaminant in these types of yarns is silica. These impurities in the yarns can abrade needles. The consequences of needle wear include needle lines, unintended holes in the fabric, unintended tuck stitches, unintended double stitches, yarn breakage, machine stops and downtime. These consequences result in defective products and increase the time for manufacture and the cost of wearable articles that incorporate textile-based electrodes.
Other limitations can also be present, for example, when biophysical monitoring via electrical contact with the corpus is desired. These limitations may include the difficulty of making metallic wires or yarns with metallic fibers part of a traditionally fabricated textile due to the fragility and durable flexibility of metal wires and yarns with metal fibers.
Other configurations may also suffer certain limitations. For example, configurations incorporating “folded over” and partially overlapping layers of electrically conductive material (with electrically insulative material arranged to electrically isolate the electrically conductive material) may severely limit the freedom to design the placement of electrodes integrated with a garment or textile article.
Accordingly, there exists a need to provide a textile-based electrode capable of overcoming one or more of the deficiencies of the prior art.